I. Field Of The Invention
The invention relates to an improved sealing assembly for a window in gauges, meters and other accessories over a wide range of temperature and environmental conditions.
II. Description Of The Prior Art
Many types of accessory equipment, such as gauges and meters are exposed to a variety of external conditions which are detrimental to the operation of the device. Devices of this type necessarily include a housing for the works of the device to which is secured a window through which the status of the gauge can be read by an operator. In particular, natural gas meters must have a window through which the utility company or supplier can determine the meter reading periodically in order to determine the correct amount used. Gas meters are normally located outside of dwellings and so must withstand the ravages of temperature from winter to summer. The seal assembly must secure the internal components from moisture, and in the case of natural gas meters, prevent oil contained in the unit from escaping and leading to a stopped meter or inaccurate readings. The gas meters are usually unpressurized meters.
Such meters may have a housing with a observers window oriented in a horizontal position or they may be installed with the observers window oriented in a vertical position, or in some cases devices having windows may be moved to a variety of positions which exacerbates the problem of containing internal fluids necessary for the operation of the device.
It has been common to utilize a form of O-ring in a ring retaining groove located around the face of the gauge or meter between a housing and the edge of a window member to provide a seal therebetween. This requires compression of the O-ring between the upper and/or lower portions to bulge the O-ring out into an oval-shape to secure the required seal between the housing and the window member. The O-ring often must be made of stout material in order to survive for an extended period of time. It must resist deformation in order to provide an adequate seal. The resistance to deformation generates substantial forces in a radial direction of the edges of the window or cover which tends to either require excessive thicknesses of window material to withstand the forces generated or using a lesser compression of the seal member and risk losing the seal over time.
In recent years such windows are made from polycarbonate material which has a tendency to craze or crack over time when exposed to excessive stress. Compounding the problem is the differential rate of expansion and contraction of the metallic members and the plastic cover window which can become significant over a temperature range of approximately -40.degree. F. (-40.degree. C.) to +140.degree. F. (+59.4.degree. C.) over an extended period of time. In addition, O-rings are difficult to install in this kind of device.
The present invention provides an improved seal structure to maintain an external and internal seal over an extended period of time and range of temperature variation while at the same time producing only a very limited stress in a window which is sealed in a housing. Essentially only axial or radial forces are involved in creating the seal with expansion and contraction being provided for by the seal itself. The seal is easy to install and does not require high vertical compressive forces to effectuate a sufficient seal.